A bearing decelerator comprises a bearing; a retardance ring is arranged on a bearing inner ring, and provided with a reverser; the reverser is connected with an outer ring, and provided with a hairbrush; the retardance ring is connected with a rotary shaft; the hairbrush can decelerate and protect the bearing from being damaged; the rotary shaft decelerates and drives the retardance ring; the retardance ring drives an orientation device to decelerate, and the hairbrush enlarges friction force until stops, thus enlarging frictional force; the bearing decelerator can decelerate and prevent wearing.